for knowledge of t attacks, as court records were unsealed white house defended fbi investigation of tamerlan tsarnaev in 2011, two years before boston bombings after a tip from russia an government claimed that 26-year-old of a follower of radical islam. >> we have a process in this country we have to find grounds for action, fbi did an investigation and did not find grounds at the time. >> reporter: investigators are doing a deep dive on tamerlan tsarnaev's 6 month trip to russia last year, and whether he had direct contact with terrort in the regn. they has possible leads to the group one known at ama rat in in 2007. >> fbi was you an aware of old pro either's trip in 2012, based on a briefing, they suspect brothers had outside help. >> the fbi and cia and every intelligence agent we had is struggling to figure out what coming next. fbi informed russian that bureau had not found any derogatory information on oile older brother and requested immediate help. >> thank you very much. lou: authorities are searching for hundreds of answers many they hope tsarnaev will answer it is important to u